If you are running exchange 2000/2003, this is pretty straight forward.
You first need to make sure you set your mailbox store policy to retain deleted mailboxes for 30 days or so.
Then you delete the users old user account from AD, in effect orphaning the mailbox.
You then create a new user account, without a mailbox.
You then "reconnect" the old orphaned mailbox to the new user account.

Not to quibble, but what's with the "B".......was there information you needed to do this that I left out?

From the EE Help guidelines:
What Grade should I give?

Ask 10 Experts this question, and you'll get 10 different answers. One thing is certain: Grading at Experts Exchange is NOT like school. Here's what EE says:
Although we use an A-D scale here at Experts Exchange, it works differently than, say, school grades. If one or more Experts' proposals are accepted as answers, they should usually be given an A or B grade, since they have taken the time to provide you with a working solution. If a possible solution is incomplete - ask for clarification or details before accepting the answer and grading it. People should not be given lower grades because of incorrect grammar or because you just accepted their answer or comment to close the question. Keep in mind, your question and any follow-up comments should be focused so that there can be a specific answer. The following is a good guideline to follow when grading:

A: The Expert(s) either provided you with a thorough answer or they provided you with a link to information that thoroughly answered your question. An "A" can also be given to any answer that you found informative or enlightening beyond the direct question that you asked.

B: The Expert(s) provided an acceptable solution, or a link to an acceptable solution, that you were able to use, although you may have needed a bit more information to complete the task.

C: Because Experts' reliability are often judged by their grading records, many Experts would like the opportunity to clarify if you have questions about their solutions. If you have given the Expert(s) ample time to respond to your clarification posts and you have responded to each of their posts providing requested information; or if the answers, after clarification, lack finality or do not completely address the issue presented, then a "C" grade is an option. You also have the option here of just asking Community Support to delete the question.

Remember, the Expert helping you today is probably going to be helping you next time you post a question. Give them a fair chance to earn an 'Excellent!' grade and they'll provide you with some amazing support. It's also true that a "C" is the lowest grade you can give, and the Experts know that -- so use it judiciously.
Only the Moderators have the choice to give a D grade. Beyond that, in a practical sense, the grading guidelines have "softened" a bit over the last year or two; one might expect that the majority of grades would be Bs (a standard "bell" curve), but the fact is that the culture of the site has caused there to be an inordinately high percentage of As. The Moderators have been instructed to ensure that the As they award are actually "Excellent" answers. Similarly, the C grade is the lowest that can be given by a member, a fact which should be kept in mind when grading as well. The use of a C in a vindictive manner is likely to be changed by a Moderator. You may not like the answer you get, and in some cases, and you may not like the way it is delivered, but if it is deemed to be accurate, no less than a B is an acceptable grade.

Can I get a grade changed?

If you are the person who asked the question, then yes, you can, by asking the Moderators to change the grade -- although they won't be inclined to lower it.

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